Ridge

ARMA's Residential Asphalt Roofing Manual defines the term this way: “Ridge: The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.” The FRSA-TRI Florida High Wind Concrete and Clay Tile Installation Manual, written for tile, uses almost the same wording: “The uppermost horizontal external angle formed by the intersection of two sloping planes of the roof.” One manual is for asphalt shingle and the other for concrete and clay tile, and on this word they agree.

Three words in that definition do the work. Uppermost puts the ridge above every other line on the roof. Horizontal separates it from a hip, which is also an external angle but runs downhill from the ridge to the eaves. External means the two planes fall away from the line, the opposite of a valley, which both glossaries define as the internal angle where two sloping planes meet.

The ridge is also the fixed point that roof measurements start from. ARMA defines rise as “the vertical distance from the eaves line to the ridge,” one of the lengths that roof pitch and slope are built from; how each body turns those lengths into a figure belongs to that entry.

Not every roof has a ridge. ARMA's manual describes a shed roof as a roof with one sloping plane that has “no hips, ridges, valleys or gables.” Nor does a ridge tell anyone how steep the planes below it are. Steepness is a separate measure, and OSHA sorts a low-slope roof from a steep roof by that measure alone.

The ridge appears in two cleaning documents, and neither one is about the ridge itself. GAF's technical bulletin on algae staining uses it as a landmark. GAF says the stains are often caused by the cyanobacteria Gloeocapsa magma, and that blue-green algae “appear as dark stains on shingles that usually cover more area on the lower section of the roof and taper as they reach the ridge.” In that description the ridge is where the typical pattern is thinnest.

GAF adds that the growth generally favors the northern exposures of a roof, which receive less sunlight. Why a streak runs heavier low on one slope is the subject of why roof algae grows on the north side, and the pattern as a whole is described in what the black streaks on a roof are.

The second document is Eagle Roofing Products' 2025 article on walking a tile roof, which uses the ridge as a compass for the feet: “Orient your feet in a direction parallel with the ridge and try to distribute your weight evenly, walking as softly as possible.” TRI Alliance's Roof Maintenance Guide gives the same orientation in other words, telling a walker to orient the feet in a horizontal direction. The rest of that technique is not part of what a ridge is, and it is not repeated here.

Being the uppermost line on a sloped roof, the ridge is also the part of it farthest above the ground, so any work near it is work at height, which is where fall protection comes in.